Safety door for drawout switchgear



June 11, 1957 J. D. WOOD SAFETY DOOR FUR D RAWOUT SWITCHGEAR 2 Shets-Sheet 1 Filed Dec. 12, 1955 .7 INVENTOR. JOSEPH 9.. W000 June 11, 1957 J. D. WOOD SAFETY DOOR FOR DRAWOUT SWITCHGEAR Filed Dec. 12, 1955 A INVENTOR. JOSEPH 0. W000 BY W V ATTaQ/ H Breaker Company, Philadelphia, Pin, a "corporation of Pennsylvania I I Application'Decernber' 12', 1955 Serial No, 552,556 3 Claims. (Cl: 31799) I My invention relates to drawout switchgear, and more particularly is directed to a novel arrangement wherein access to the drawout apparatus within the housing is prevented until the apparatus is grounded.

In electrical switch gear, it is usually desirable to provide a metal clad housing for the equipment and mount the equipment in a drawout arrangement so that inspection and replacement of parts is simplified. Generally it is desirable to prevent access while the equipment is being energized by the main source. In the known prior art this is generally achieved by mountingthe electrical apparatus on rollers, which in turn are slidably mounted on rails with a link connection betweenthe' door or covering of the housing of the apparatus. When an attempt is made to open the door, the link connected between it and the apparatus will force the apparatus to 1011' forward so as to become de-energized. Thus, an operator, theoretically, cannot gain access to the equipment while it is being energized from the main source.

In order to provide further adequate safety for operating personnel, the equipment when moved from the energized position to the non-energized drawout position is usually brought into contact with a grounding bus so that the electrical apparatus is electrically grounded. That is, to ensure absolute protection to operating personnel and equipment, it is necessary to p'rovide'automatic grounding means for the equipment when it is in the drawout position.

In the prior art arrangement, as above noted, adequate protection has been provided to prevent'operating personnel from gaining access to the equipment while it is being energized, and also adequate means have been provided to ground equipment when it is in a drawn out position. However, prior art arrangement has notprovided an adequate safetyrneans to protect personnel from danger when the electrical equipment is between its energized position and the fully drawn out position. That is, in the event an operator should start to drawout the equipment and stops between the energized position of the apparatus and the fully drawn out position of the apparatus, the equipment willnot be grounded. This unfavorable condition exists wherein the operator has access to the ungrounded apparatus. However, since the housing door or cover is now partially open, the operator will have access to the non-grounded interior apparatus.

My invention is directed to drawout type apparatus wherein access to the equipment within the metal clad housing is prevented until the equipment is completely grounded. I achieve this result by providing a safety door in addition to the main door or cover of the housing.

In my novel construction, the safety door is positioned between the main door of the housingand the apparatus contained within the housing in a manner to prevent access to the interior while the safety door is closed. The safety door is positioned with respect to the main door of the housing so that it cannot be opened until the main door is in a fully open position, at which time the internal equipment will be in contact with the grounding bus and,

United States Patent 2,795,739 Patented June 11, 1957 therefore, adequately grounded. It is only at this time that the operator can open the safety door to thereby gain access to the now grounded equipment contained within the housing.

Accordingly, a primary object of my invention is to provide a novel drawout apparatus arrangement wherein safety means are provided to prevent access to the equipment within until the internal equipment is grounded.

Still another object of my invention is to provide a safety arrangement for drawout apparatus wherein access to the equipment contained within the housing is prevented as long as the equipment is not grounded, even though it is not energized from the main source. A still further object is to provide a safety door for drawoutmechanisrn which interlocks with the main door of the housing-in such a manner that the safety door cannotbe opened until the main door is fully opened, at whichtime the internal equipment is automatically grounded.

These and other objects of my invention will be apparent when taken in connection with the drawings in which:

Figure 1 is a side view, in section, of the drawout apparatus contained in my invention. This view shows the electrical apparatus contained within in the energized position, andthus, both the safety door and main door of the enclosure are in the closed position.

Figure 2. is a side view, in section, of the apparatus of Figure l and illustrates the position of the various components when the internal apparatus is partially drawn out. In the solid view of Figure 2 the apparatus is between the energized position and the grounded position. In the dotted view of Figure 2, I have shown the position of the components when the apparatus is in the grounded position.

The switch gear structure 10 is comprised of a metal clad housing 11 having electrical apparatus 12 positioned therein. For the purpose of illustration, I have shown the electrical apparatus as being comprised of a potential transformer 13 and a fuse 14. The electrical apparatus 12 is mounted on and contained within the housing 11. This is achieved by providing rollers 16 and 17 for the "structure 15 which slide within the rails 18. The electrical terminal 19 contained within the bushing 20 is electrically connected to the main stationary disconnect contact 21. The electrical apparatus 12 is provided with a movable disconnect contact 22 which is biased upward by means of the spring 23. Therefore, in the position illustrated in Figure 1, the electrical apparatus 12 is energized from the main source. At the front of the housing 11, which is at the left in Figures 1 and 2, there is provided a main door 24 which is pivotally mounted on the housing at point 25. An operating link 26 pivotally mounted at the door at 27 and pivotally mounted at the electrical apparatus 12 at point 28 provides an interlock between the cover 24 and the electrical apparatus 12. Thus, when the door 24 is moved from the fully closed position of Figure 1 toward the fully open position (as indicated in the dotted view of Figure 2). The operating link 26 draws out the electrical apparatus'12. That is, since the electrical apparatus 12 is slidably mounted on the rail 18 by means of its rollers 16 and 17, this unit will be slidably drawn out if the door 24 is moved from the closed position of Figure 1 through the position illustrated in Figure 2 to the fully open position illustrated in the dotted view of Figure 2. As is well known in the switch gear art, it is essential, in order to provide adequate protection to operating personnel, to ensure that the apparatus 12 is grounded as it is drawn out. To this end a grounding bus 30 is positioned in the path of movement of the movable disconnect contact 22. Thus, as illustrated in 3 the figures, as the door 24 is moved from the fully closed to the intermediate position, the contact 22 will slide off the stationary main contact 21 so that the electrical equipment 12 will be de-energized. However, upon further movement of the main door 24 to a fully open position, as illustrated in the dotted view of Figure 2, the movable contact 22 will run into electrical engagement with the stationary grounding bus 30, thereby grounding electrical apparatus 12.

It will be noted that when the main door 24 is in the fully closed position, that is when the electrical apparatus 12 is energized, that one cannot gain access to the interior of the housing 11.

Due to the interlock arrangement between the main door 24 of the electrical apparatus 12, by means of a connecting link 26, an operator attempting to gain access to the interior of the housing 11 would automatically disconnect the electrical apparatus 12 from the contact 21 before gain is accessed. However, as illustrated in the solid view of Figure 2, it is possible that the operator may move the main door 24 only part of the distance between the fully closed and the fully open position, and during this time the electrical apparatus is neither in electrical engagement with the main contacts nor grounded bus. In the prior art arrangements, it was possible for the operator to gain access to the interior of the housing 11 during this period of time and thus expose himself to ungrounded electrical equipment.

My invention is directed to this particular condition to prevent access by the operator While the equipment is in the inbetween position illustrated in Figure 2. In order to achieve this safety feature, I provide a safety door 31 which is pivotally mounted at 32 on the housing 11. The safety door 31 has a link 33 pivotally mounted at one of its ends at 34 with the other end slidably mounted and guided for movement within a groove at the left end of the housing 11 where link 33 may be held fast to prevent the safety door from closing while the operator is working on the electrical apparatus 12. The slide mounting and holding of link 33 is done in a manner Well known in the art. The safety door 31 is positioned between the main door 24 of the electrical apparatus 12, and so positioned that the main door 24 is within the path of movement of the safety door as it is moved from the fully closed position of Figure 1 to the fully open As has heretofore been noted, as the main door 24 is rotated about its pivot 25 in the closed position of Figure 1 to the open position illustrated in Figure 2, the electrical apparatus 12 will be drawn out toward the grounded position. Since an over travel movement is provided on the grounded contact 30, the electrical equipment will be grounded. The linked and pivotal relation between the main door 24 and the safety door 31 is such that the main door 24 lies in the path of movement of the safety door 31 when the main door is in any position which does not correspond to the grounded position of the equipment. That is, the interlock arrangement between the main door 24 of the electrical apparatus 12 is such that only when the electrical apparatus 12 is in electrical engagement with the grounding bus 30, that the main door 24 no longer obstructs movement of the safety door 31 from the fully closed position to the fully open position. However, at any time prior to engagement of contacts 22 of electrical apparatus 12 with the grounding bus 30, the main door 24 will obstruct movement of the safety door 31 to the open position. Thus, during this period of time the operator will not have access to the electrical apparatus 12 contained within the housing 11. Figure 2, however, illustrated this specific safety condition wherein the main movable contact 22 has been drawn out to a position between its fully energized position in contact with contact 21 and its grounded position in contact with grounded bus 30. It is in this position that it is essential to prevent access of position of the dotted view of Figure 2.

"the operator to the interior portion of the housing 11.

Thus, since the safety door 31 cannot be opened due to the positioning of the main door 24 in the path thereof, access to the electrical apparatus 12 is prevented. It is only after the electrical apparatus 12, as heretofore fully described, has been .moved to the fully grounded position, as illustrated in the dotted view of Figlre 2, that the safety door 31 can be moved to the fully open position so that the operator gains access thereto.

In the foregoing, I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein but only by the appending claims.

I claim:

1. An'electrical switchgear structure being comprised of a housing and electrical apparatus; said electrical apparatus being slidably mounted within said housing, said housing having a main door for gaining access to the interior of said housing and having a closed and open position, said main door being operatively connected to said electrical apparatus, said electrical apparatus moved from an energized position to a grounded position by said operative connection when said main door is moved from said closed position to said open position; a safety door positioned between said main door and said electrical apparatus, said safety door having a closed position and an open position, said main door preventing movement of said safety door from said closed position to said open position until said main door is in said fully open position.

2. An electrical switchgear structure being comprised of a housing and electrical apparatus; said electrical apparatus being slidably mounted within said housing, said housing having a main door for gaining access to the interior of said housing and having a closed and open position, said main door being operatively connected to said electrical apparatus, said electrical apparatus moved from an energized position to a grounded position by said operative connection when said main door is moved from said closed position to said open position; a safety door mounted on said housing between said main door and said electrical apparatus, said safety door having a closed position and an open position, an interlock between said safety door and said main door to prevent movement of said safety door from said closed position to said open position when said electrical apparatus is not in said grounded position.

3. An electrical switchgear structure being comprised of a housing and electrical apparatus; said electrical apparatus being slidably mounted within said housing, said housing having a main door for gaining access to the interior of said housing and having a closed and open position, said main door being operatively connected to said electrical apparatus, said electrical apparatus moved from an energized position to a grounded position by said operative connection when said main door is moved from said closed position to said open position; a safety door pivotally mounted on said housing between said main door and said electrical apparatus, said safety door having a closed position and an open position, said safety door preventing access to said electrical apparatus while said door is in said closed position, said main door preventing movement of said safety door from said closed position to said open position until said electrical apparatus is in said grounded position.

References Cited in the file of this patent UNITED STATES PATENTS 224,302 Morrison Feb. 10, 1880 2,151,756 Fletcher et al Mar. 28, 1939 2,689,293 Claybourn et al Sept. 14, 1954 

